A method of forming a conductive Ga2O3 crystal film on a crystal substrate such as sapphire substrate by heteroepitaxial growth is known as a conventional method for producing a Ga2O3 based crystal film (see e.g. PTL 1). PTL 1 discloses that a Ga2O3 crystal film is formed using an MBE method and Sn is used as a conductive impurity for imparting conductivity to the Ga2O3 crystal film.